The invention relates to a valve system for the pre-engagement unit of a braking pressure modulator.
European patent application A1-0 893 636 discloses a hydraulic solenoid valve, which utilizes an elastic means to compensate for mechanical tolerances and heat expansion.
This known patent application shows a valve cartridge 1 in FIG. 1 which contains the elements of mechanical actuation. This valve cartridge is inserted into an opening of another component, which contains a magnet coil 13.
When current flows in the magnet coil (13), a magnetic field is created in the closed magnetic circuit, consisting of the parts referenced in FIG. 1 as 14, 2, 7 and 9. This magnetic field causes a force to be exerted upon a core 9 constructed in the form of an armature. This force also acts, via a ram 16 connected to the core, upon a ball 17 which is not connected to the ram 16. The ball 17 is lifted up against the force of a spring 22 from its sealing seat 18 causing the sealing seat 18 to be opened. (When there is no current flowing in magnet coil 13, ram 16 is held lightly, via a fixing spring, on the ball 17, as explained below, whereas spring 22 is significantly stronger).
When sealing seat 18 is opened, the connecting channel between the hydraulic inlet (therein 20) and the hydraulic output terminal (therein 21) is opened. Therefore, the known solenoid valve can be described as a normally closed 2/2-way solenoid valve.
Since the known solenoid valve is made up of several separate parts, a number of different work steps are required in order to assemble it.
As shown in FIG. 1, valve cartridge 1 is inserted into an opening of a bearing block 3, which is configured in the form of a hydraulic block. The flange 2 is then placed over bearing block 3, so that both flange 2 and valve cartridge 1 are attached to bearing block 3 by the conical widening part 6. As such, a separate component, consisting of bearing block 3, valve cartridge 1, and flange 2, is pre-assembled, and is contained within the overall hydraulic system.
In the electrical portion of the known solenoid valve (FIG. 1), a separate coil 13 is installed in a frame yoke 14, together with the elastic blocks 33 and 34, and a plastic frame 24. A rubber part 32 is then inserted between frame yoke 14 and the upper wall 29 of the valve housing. Then, the completed assembly, consisting of frame yoke 14, coil 13, and elastic blocks 33 and 34, is installed so that the terminals of coil 13 extend through the contacting bores of the computer board 26.
The pre-assembled component, consisting of bearing block 3, valve cartridge 1 and flange 2, is now screwed on to the valve housing, such that elastic block 33 presses against flange plate 2. This screw connection causes the participating elements in the electrical portion to be placed under tension, which causes coil 13 to be placed in a longitudinal axial alignment relative to the rest of the structure. The terminals of coil 13 are rigidly connected in this longitudinal alignment; e.g., by soldering (27) to computer board 26. As a result, the longitudinal alignment is made permanent.
Permanent longitudinal fixing in conjunction with elastic elements can be problematic, however, since a change in the force relationships among the tolerance compensating elements (e.g., as a result of temperature influences) does not take into account the long-term behavior of elastic elements, or the influences caused by forces of inertia due to oscillations.
The assembly of valve cartridge 1 also requires several work phases. First, movable core 9 with ram 16 and the fixing spring (no reference number is provided), are introduced into a tube 11, which is used as an armature guide. Next, the inner part 7 is inserted and attached with the spacer 10 via its smaller diameter upper part 8. Then, a sealing seat element (no reference number is provided) is pressed into inner part 7 over the sealing ball 17, which includes a guide (no reference number is provided). Finally, it is necessary to assemble a pressure element (no reference number is provided) for ball 17 and spring 22, which pre-stresses this pressure element.
Typically, in the case of a braking pressure modulator application, additional valve variants, such as a normally open 2/2-way solenoid valve, or a 3/2-way solenoid valve, must be used in addition to a normally closed 2/2-way solenoid valve. However, no mention of these valve variants is made in the cited patent application.
It is therefore the object of the invention to provide a valve cartridge system suitable for a pre-engagement unit of a braking pressure modulator, in which the valve cartridge assembly is facilitated, while at the same time eliminating the need for elastic tolerance-compensating elements.
This object is achieved in a valve system for the pre-engagement unit of a braking pressure modulator. The inventive valve system comprises a one-piece housing, in which a square-shaped opening forms a first forked flange and a second forked flange. A first bore in the first forked flange is axially aligned with a second pocket bore in the second forked flange. A magnet coil, having an opening in the form of a straight circular cylinder, is positioned within the square-shaped opening of the housing. A valve cartridge, in the form of a cylinder with circular cross-section, is inserted into the housing from the first bore in the direction of the second pocket bore, so that the magnet coil can only be displaced in an axial direction. In addition, at least one pressure medium terminal is connected to at least one of the forked flanges.
One advantage of the present invention is that the valve cartridge can be assembled as a pre-testable component prior to installation in the housing, and that it can be replaced with another valve cartridge without adjustment.
In a further development of the invention, the valve cartridge is a solenoid valve cartridge actuated by a magnet coil, the solenoid valve cartridge comprising three individual cylindrical bodies connected end-to-end with no increase in cylinder diameter in an assembly direction so as to form an integral unit. The second cylinder body is hollow and contains an armature and an armature return device. The first and third cylinder bodies are optionally equipped with either sealing seats or armature stops. When there is no current flowing in the magnet coil, the armature of the second cylinder body presses against first cylinder body. Where there is current flowing in the magnet coil, the resultant magnetic field causes the armature to press against the third cylinder body.
A further advantage of the present invention is that components of the same type, e.g., armatures, valve bodies, and magnet coils, can be used interchangeably in different valve systems, thus reducing manufacturing costs.